1. Field of the Invention
The present invention relates to a disk drive for recording data on and reproducing data from a recording medium such as an FD (flexible disk), CD (compact disk), or MO (magneto-optical disk), and in particular to a semiconductor integrated circuit device for use in such a disk drive to control the driving of a spindle motor and a stepping motor provided within the disk drive while detecting the temperature inside the disk drive.
2. Description of the Prior Art
FIG. 1 shows a disk drive having a head 2 for writing and reading signals to and from a recording medium 5 such as an FD or CD, a spindle motor 3 for rotating the medium 5, a stepping motor 4 for moving the head 2 radially across the medium 5, and a semiconductor integrated circuit device 1 designed for use in a disk drive to record data on and reproduce data from the medium 5 through the head 2 and to control the driving of the spindle motor 3 and the stepping motor 4.
FIG. 6 shows the internal configuration of a conventional semiconductor integrated circuit device designed for use in such a disk drive. The semiconductor integrated circuit device 1' for use in a disk drive (hereinafter referred to simply as the "semiconductor integrated circuit device 1'") shown in FIG. 6 has a read/write section 6 for writing and reading signals to and from the medium 5 (FIG. 1) through the head 2 (FIG. 1), a spindle motor driver section 7 for controlling the driving of the spindle motor 3 (FIG. 1), a stepping motor driver section 8 for controlling the driving of the stepping motor 4 (FIG. 1), temperature detection sections 9a and 9b for detecting the temperature inside the semiconductor integrated circuit device 1', and a control section 10 that exchanges signals with the individual blocks mentioned just above.
In this semiconductor integrated circuit device 1', the spindle motor 3 and the stepping motor 4 are driven in such a way that the head 2 is moved to a position specified by the control section 10 to allow writing or reading of a signal at that position on the medium 5. At this time, the spindle motor driver section 7 and the stepping motor driver section 8 operate concurrently, and thus the temperature inside the semiconductor integrated circuit device 1' rises most steeply. If this condition persists, and the temperature inside the semiconductor integrated circuit device 1' keeps rising, the semiconductor integrated circuit device 1' is in danger of malfunctioning or destruction. For this reason, it is essential to lower the temperature inside the semiconductor integrated circuit device 1' by stopping the operation of the spindle motor driver section 7 or the stepping motor driver section 8 when the temperature reaches a predetermined level.
To achieve this, when the temperature inside the semiconductor integrated circuit device 1' rises to T1.sup.+ as shown at (a) in FIG. 7, a signal TSD1 that the temperature detection section 9a outputs to the control section 10 is turned to a high level as shown at (b) in FIG. 7 to request the spindle motor driver section 7 to be turned off. Thus, when the signal TSD1 is turned to a high level, the control section 10 controls the spindle motor driver section 7 to stop its operation. Thereafter, when the temperature inside the semiconductor integrated circuit device 1' rises further to T2.sup.+, a signal TSD2 that the temperature detection section 9b outputs to the control section 10 is turned to a high level as shown at (c) in FIG. 7 to request the stepping motor driver section 8 to be turned off. Thus, when the signal TSD2 is turned to a high level, the control section 10 controls the stepping motor driver section 8 to stop its operation.
A while after the spindle motor driver section 7 and the stepping motor driver section 8 have been stopped in this way, the temperature inside the semiconductor integrated circuit device 1' starts dropping as shown at (a) in FIG. 7. When the temperature drops to T2.sup.-, the signal TSD2 that the temperature detection section 9b outputs to the control section 10 is turned to a low level as shown at (c) in FIG. 7 to request the stepping motor driver section 8 to be activated. Thus, when the signal TSD2 is turned to a low level, the control section 10 controls the stepping motor driver section 8 to start its operation. Thereafter, when the temperature inside the semiconductor integrated circuit device 1' drops further to T1.sup.-, the signal TSD1 that the temperature detection section 9a outputs to the control section 10 is turned to a low level as shown at (b) in FIG. 7 to request the spindle motor driver section 7 to be activated. Thus, when the signal TSD1 is turned to a low level, the control section 10 controls the spindle motor driver section 7 to start its operation.
In this way, when the temperature reaches a predetermined level, the spindle motor driver section 7 and the stepping motor driver section 8 are stopped to prevent malfunctioning or destruction of the semiconductor integrated circuit device 1' resulting from high temperature inside it.
As shown in FIG. 7, the timing with which the spindle motor driver section 7 and the stepping motor driver section 8 are turned on or off depends on the rate at which the temperature inside the semiconductor integrated circuit device 1' varies. Therefore, depending on the environment in which the semiconductor integrated circuit device 1' is used, the temperature inside it may vary at a very steep rate as shown in FIG. 8. In such a case, the signals TSD1 and TSD2 that the temperature detection sections 9a and 9b respectively output are turned from a high level to a low level or from a low level to a high level almost at the same time.
Turning the states of the signals TSD1 and TSD2 almost at the same time in this way results in the spindle motor driver section 7 and the stepping motor driver section 8 being turned on or off almost at the same time. As a result, a large current suddenly starts or stops flowing into the semiconductor integrated circuit device 1'. At such moments, in particular when a large current suddenly starts flowing in, the voltage supplied to the semiconductor integrated circuit device 1' may fluctuate and cause unstable operation thereof, leading even to destruction of the internal circuit thereof. Moreover, the temperature detection section for detecting the temperature at which the spindle motor driver section 7 is to be turned on or off and the temperature detection section for detecting the temperature at which the stepping motor driver section 8 is to be turned on or off need to be provided separately, like the temperature detection sections 9a and 9b, and this hinders the miniaturization of the chip size.